A lot of techy Neo questions

What's the difference between V1X and V2X PCM ROMs on early games? Each type has their own bus, do they each correspond to different YM2610 ports?

The NEO-PCM chip used in all games after 1992 or so appears to be able to service both buses (V1X and V2X) with a single V ROM using a smart latching design. Can you convert V1X and V2X to VX ROMs or did the NEO-PCM do away with V2X ROMs altogether? For example if I wanted to move an ancient game to a newer board, can I without modifying the PCM's logic?

I know that some bootlegs have a NEO-PCM equivalent circuit of 8 x 8-bit registers, 8-bit latch, 4-bit counter and some inverters. Does anyone here know the logic?

Which games are pre-Phantom-1 MVS->home converters not compatible with? How many Phantom-1 models are there and what does the latest one support that the earlier didn't?

In the Super MVS Converter II are there any chips besides the Altera CPLD? Does it have an oscillator? What is the adjustment screw actually for? Adjusting timing?

Does anyone here know the logic for the PRO-CT0 aka ALPHA-8921 or the NEO-ZMC2 chip?

Does anyone know what the PRO-CT0's test pins do?

Neo can address at least 512M of C ROM without external bankswitching, does it do this via internal bankswitching like it does for P ROMs or is there really a 24+ bit tile space (24-bit address x 32-bit data = 512M)?

Thanks

Very techy for this forum.
More a question for mame dev. Maybe Raz could shine some light here.

Kyuusaku said:

Neo can address at least 512M of C ROM without external bankswitching, does it do this via internal bankswitching like it does for P ROMs or is there really a 24+ bit tile space (24-bit address x 32-bit data = 512M)?

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I think I can answer this one. There is no C ROM bankswitching, with later games tiles can be pulled from anywhere within the C ROM space and displayed without limitation.

Thanks! Do you know what the tile limit is though? By looking at the home cartridge connector, there appears to be pins for 6 more address lines after 512M (for 4GiB of tiles), but the pattern suggests there are only 2 more to get 2 gigabits of character ROM, dunno though.

I've looked at MAME and some other emulator source but they're too abstract to learn anything about the system's physical implementation. If anyone knows which if any MAME devs have done Neo reverse engineering, I'd like to look them up

im curiuos why all the questions. you making a flash cart? if so i want to beta test one

Not really, I'm interested in building my own development hardware, and perhaps in the future publishing unlicensed games without sacrificing original carts.

I also want to give away the logic for a MVS->home converter in hopes that they can be produced more competitively since they contain no more than US$15 of parts.

Kyuusaku said:

Thanks! Do you know what the tile limit is though? By looking at the home cartridge connector, there appears to be pins for 6 more address lines after 512M (for 4GiB of tiles), but the pattern suggests there are only 2 more to get 2 gigabits of character ROM, dunno though.

I've looked at MAME and some other emulator source but they're too abstract to learn anything about the system's physical implementation. If anyone knows which if any MAME devs have done Neo reverse engineering, I'd like to look them up

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I think the tile limit depends of the cart type. The limit I have seen used in an original NeoGeo game is 64megabytes of C ROM data although in theory this can be doubled because there is still a free line in the sprite table.

What is intresting is the way some games use larger than normal 8x8 tile data space (some games use 512k instead of 128k). The intresting part is the fact that their are 2 different methods this data is fetched from the cart in the programming of the VRAM. How this is achieved I am not sure as both methods are quite different.

You may find http://cgfm2.emuviews.com/temp/mvstech.txt intresting if you have not already seen it.

Kyuusaku said:

Not really, I'm interested in building my own development hardware, and perhaps in the future publishing unlicensed games without sacrificing original carts.

I also want to give away the logic for a MVS->home converter in hopes that they can be produced more competitively since they contain no more than US$15 of parts.

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You may be intrested that the next universe bios will bring the ability to upload and download data to a NeoGeo via a cable connected to its 2up joystick port and a PC. Of course one is limited to working with the NeoGeo's RAM only (you cannot change gfx tiles for example) but you can execute your own code which will bring the ability for homebrew demos and smaller homebrew games with music and tiles based on carts plugged into the system.

The NeoGeo CD has the ability to be converted into a nifty little DEV test system although your limited in the ammount of tile space it has.

Razoola said:

The NeoGeo CD has the ability to be converted into a nifty little DEV test system although your limited in the ammount of tile space it has.

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really do tell

werejag said:

really do tell

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Well I assume anyone wanting to dev stuff on the neogeo would actually use emulation first. The advantage of the NeoGeo CD is that everything gets loaded from CD which saves one from having to Burn EPROMs etc. One would simply need to replace the Bios in the NeoGeo CD to something more like an AES. IE; it would simply load everything from the CD into RAM once at the start and then make the system operate as if it were an AES from that point.

The bios could also take care of the niggly litle problems (byteswapping and swapping IRQ2 and 3 addresses). I suspect the bios can also be altered to load files that are more in a cart type format too.

Razoola said:

You may find http://cgfm2.emuviews.com/temp/mvstech.txt intresting if you have not already seen it.

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I do, thanks!

Kyuusaku said:

I do, thanks!

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You will note in the sprite info that there is one unknown bit. I believe this bit would be the final high bit of the sprite tile number (bit 19). No game has ever used it however.